The present invention is directed to an arrangement for a distributive feedback (DFB) laser as an optically stabilized feedback amplifier.
An arrangement wherein a (positive) feedback is achieved with optical radiation into a DFB laser is disclosed in an article by H. Kawaguchi et al entitled "Tunable Optical-Wavelength Conversion Using an Optically Triggerable Multielectrode Distributed Feedback Laser Diode", IEEE Journal of Quantum Electronics, Vol 24, No. 11, November 1988, pp. 2153-2159. This article describes a DFB laser having a saturatable absorber, whose effect is that the DFB laser operating below the laser threshold can be activated by a beamed-in light. This apparatus is also provided for wavelength tuning.
U.S. Pat. No. 4,736,164, whose disclosure is incorporated herein by reference thereto and which claims priority from the same two applications in the United Kingdom as published European Specification 0 174 729, discloses a method for amplifying an optical signal. The method comprises infeed of an optical signal to be amplified into the active layer of a semiconductor laser structure, through which a driver current flows, whereby an amplified signal is emitted by the active layer, and whereby, in this method, the wavelength .lambda..sub.M of the amplification maximum given this driver current for the lower power limit of the optical input power a longer .lambda..sub.UPPER of the two wavelengths given zero amplification with the drive current for the lower power limit of the optical input power. The wavelength .lambda. of the optical signal to be amplified is limited by the following equation: EQU .lambda..sub.UPPER &gt;.lambda.&gt;.lambda..sub.M
An arrangement wherein a constant optical amplification is achieved by an optical radiation into a semiconductor laser is described in a publication by W. F. Kosonocky et al entitled "GaAs Laser Amplifiers", IEEE Journal of Quantum Electronics, Vol. QE-4, No. 4, April 1968, pp. 125-131. This publication describes a semiconductor laser having a Fabry-Perot resonator wherein the light to be amplified is beamed-in perpendicular to the propagation direction of the laser light.